Hygrometer



A. H. LAMB HYGROMETER June 20, 1950 Filed Oct. 11, 1945 RELATIV UMIDITY Patented June 20, 1950 2,5123% HYGROMZETER APE QQX. v1 3 glifia lam 1 s.

Appliea-tion flctober 11, 1945,Seri al No.

-strata.

This. invention relates to, ihy rometexsn and moreepartioulaltly .to-direot reading-ins ruments fonthe measurement lot relative h midit The direct reading ,hyer me ers QWi mane: faetured commercially .arei ased upon themlQn ui: tud al e pa ion of strands o n trips, o Dream? materia munon. in bs. ab rbsds at r. water yanora .iirip teafiin u file Xe humid t such .h erom ters ar t es iable? at s t r whe'i -lo t d in a ted to only small Changes y and when 'restandardized fr m im o m to qmre sa e for han es n h w istband he t eng h of e nds r, strips as theyage. The organic material may be human 1 hairQ paper or wood but is usually human hair. Although the gradual drift in calibration of such organic materials is well known, it isnot so generally known that there is a marked lack of uniformity even in supposedly identical hair type hygrorneters manu factored by the same coinpany,a1 1d that it is not possible to obtain identical operating characteristics by standardizing a series of such hairtype hygrorneters at any one relative humidity. 'Furthermore, standardization at any particular relatiye humidity will not be maintained even at that humidity value as the length and strengths of the strandsof hair will change with time.

The known deficiencies of the hygrometers with longitudinally extensible strands or-strips-ot organic material have resultedin proposals tore electrical types of -hygrometers, andsuch appara-tus maybe satisfactory for laboratory use but it isted-expensive, bulky and complex: for-,inoorporation in-small or portablehygrometers. It: was also proposed, nearly a centurysago, to-measr.

ure relative humidity by a balance havingsnonygroscopic and hygroscopic .masses located a at opposite sides. of the .axis of the balance System.

Such balance systems presumably wereeven le s s satisfactory thanith e extensible strand or strip yp of hy rometerand, so faras w We a never manufactured commercially.

Aceord ine to the pre entinv n ion, th no n.

tensionecl orotberwi'se stressed The absorbent or adsorbent materialmay; be a solid or a liquid, or mix u es of so ids and/ r l uid whi r notaffected chemi a ly by Water d i have, the reversible property of. k n up-and vin on wat r; in accordance-with cha es thee axes,

n air. conditioned space in 2." tive, humidity ofsthe atmosphere to which. they are exposed; Solid. \noneorganic adsorbents .are preferable for. .small .and/or portable hygrome ters, ebutseither. solids or liquids, maybeemployed in hygrorneters of. any desiredi size. and of portable iorvstationarymtypeu Liquids such. as triw. ethylene glycoLl lithium-. obloridenor. iodide ,or calcium, chloride-may. be held, in a i porous or fibrous mass. of. organic orjnorganic i material- 'Bheicarrienmass tmaysbeeeither hygroscopic or nonfihagitoscopiei The. weight ,of. the adsorbed waterorarater. .vapor isdirectly.imeasureduagainst a .coilerl lspring,,tt1at tends todisplace a a pointer along an. arcuate ,.seal,er.er d ated n re ative humidity; the direct measurement being. obtained by,halal-1(sillsv therfdry, w i ht of the abs rbe bysthesweight of-anoneb gro eopio Ina- Ansobiectlof .theipresen An ma ion is to ro vid idi r ct r adinahy romete s that .m y b t: coratelr alibrated andthat :maint n th i Q3111 bration. cm: wide. r n es. oi relat ve um d ty and lon reriodsa .obieet to pr v de irer met rs of. ,theidireet ead na yp lin wh h. the, ointers d aced alo aduated u: mid resale umeiweien loithena er riwater in icant ntpfl -adsmtbentlmat rialieet is to. a pror da eromet n whi h a la er is mount d upon 'aho i onta ydisposed shaman dsorb t messian a qnrh pe pp q 1 mass are ed t orp si eisidss fc h hai i and label ed sati 5999.

nee o tu n h a t and n a th torqu x te tnereenbin hewa rioawat rvam h d y e;

aaeorbentimassl M sespec aeally anm 'pt omovies.aaireetreari na hrer met in wh h mailed s r n tends adifis ee appin tr'. q

anareaatee a e. radua edt n alu s o a ive l re and th rn'naac an impre s and balan d by the (9 51 5: fi' ne Water or ate y apors: anadserbent material le vi he era-i aete ist a 0i; ubstan ia mn n te g ves off waterior water sh pe it tak s MD a v por n amoraan awi c. oil-th e: a mesnhere a e. .1-.the.I l r n aterial is exposed. p I hese l and" th m ans-and the v atae 01w sa th mama-n pa a i a v i, .i

ef he. ent al lem. 9 smearin lae n- .n; 21: 5 a .s claeleyati aq ba a s a .aiseai m ar i ma e eratism a aa a an nstrum nt a anqe ys m na ole:

the, re ative humidity;

from the folin which the activating material is of powder or granular form within an apertured container;

Fig. 4 is a side elevation of the scale plate and moving system of another embodiment;

Fig. is a front elevation of the same; and

Fig. 6 is a front elevation, with parts broken away, of a multiplier type of instrument embodying the invention.

In Figs. 1 and 2, the reference numeral l identifies a staff or shaft which is pivotally supported for angular movement by jewel bearings 2 carried by a bracket 3. A pointer assembly such as commonly employed in electrical measuring instruments is mounted on the staff I, the assembly comprising a pointer 4, threaded cross arms 5, 6 and a tail 1. The pointer 4 is movable along the arcuate scale 8 of relative humidity values which is printed or otherwise formed on the scale plate 9. A small block ill of a hygroscopic material which remains solid. and dry even at 100% relative humidity is supported on the cross arm 5, the block It being held within a wire cage constituted by the expanded turns of a spring H having a closely coiled end l2 threaded upon the cross arm. The dry weight of the piece ID of hygroscopic material is balanced by a non-hygroscopic counterweight l3 adjustably threaded on cross arm 6, and displacement of the stall I and pointer 4 is opposed by a coiled spring l4 having an inner end fixed to the staff I and an outer end adjustably anchored on the bracket 3 by an arm [5. For portable instruments, the tail 1 of the pointer assembly preferably merges into an arcuate vane I6 which moves within the air gap of adamping magnet ll.

The material Ill may be one of, or a mixture of, any of the solid dry absorbents or adsorbents which vary in weight with the relative humidity to which they are exposed, or may be a porous body or a fibrous mass impregnated or partially impregnated with a liquid which takes up and gives off water as a function of relative humidity. A number of the inorganic materials now sold commercially under various trade-marks as absorbents or adsorbents are suitable, for example silica gel, bauxite or-activated bauxite, aluminum trihydrate and the like. Other substances may be mixed with the absorbent material or materials to modify the relative humidity-adsorbed water characteristic of the mass.

The adsorbent material may be in powder or granular form to decrease the time lag between a change in relative humidity and the resultant change in the weight of the material as it takes up or gives off water for equilibrium at the new humidity value. As shown in Fig. 3, a granular mass Ill of adsorbent material or of porous material saturated or partially saturated with a water-absorbing liquid may be held in a small annular cage comprising a threaded sleeve l8 for mounting the cage on the cross arm 5 of the pointer assembly, a base 19, and a foraminous cup 20 made up from screen material of relatively small mesh secured to the sleeve l8 and base [9.

Various arrangements may be employed to support the adsorbent material and a counterbalance weight at opposite sides of the pointer stafi. As shown in Figs. 4 and 5, a shallow semi-cylindrical cage 2| for holding powdered or granular adsorbent material and a complementary semi-cylindrical balance weight 22 are mounted on the staff 23 which is supported in bearings, not shown, and provided with a calibration spring 24. A pointer 25 on the staff 23 moves along the graduated scale '26 on the annular scale plate 21. Alternatively, the annular scale plate could be supported on the staff 23 for movement of the graduated scale 26 with respect to a fixed pointer or nducial mark. The casing in which the moving system and scale plate are mounted may be a close-fitting circular casing, or it may be of any desired larger size and shape.

The scales of the direct reading hygrometers could be individually marked and graduated for each instrument, but that additional expense of manufacture is not necessary since pre-printed graduated scales may be used when the weighing springs of the instruments are of at least approximately the same strength. The volume or mass of the adsorbent material is not critical when, as described, the instruments include means for adjusting the adsorbent material towards and away from the pivotal axis to vary the effective torque arm of the water or water vapor held by the adsorbent material. Such adjustments and similar adjustment of the effective torque arm of the non-hygroscopic balance weight permit an accurate matchin of the measured humidity values to a ore-printed scale graduated in relative humidity values.

The scale graduations of the instruments illustrated in Figs. 1 and 5 are non-uniform as a full scale displacement of the pointer requires such large angular displacement of the adsorbent materialthat there is a substantial change in the effective lever or arm of the adsorbed water or water vapor. A more nearly uniform graduation of an elongated scale may be had by coupling the balance system to the pointer through a motionmultiplying gearing, thereby reducing the angular movement of the adsorbent material.

A typical construction, as shown in Fig. 6, includes a cup 20 containing adsorbent material and adjustably threaded upon the outer end of a lever 28 which is secured to a staff 29. Bearings, not shown, support the staff on a bracket 30, and a coiled spring 3i is secured to the staff and the bracket respectively. An arcuate gear 32 at the innerend of the lever 28 meshes with a pinion 33 on staff 3d which carries the pointer 35. The gear ratio may be of any desired value but is preferably such that the graduated scale 36 of about 300 extent corresponds to an angular movement of the adsorbent material of about 20 to opposite sides of its horizontalposition.

It is to be understood that the invention is not limited to the particular constructions herein shown and described 'as various changes fall within the spirit of the invention as set forth in the following claims. 1

I claim:

1. A direct reading hygrometer comprising a horizontally disposed stafi, side arms secured to and extending in opposite directions outwardly from said staff, a mass of hygroscopic material mounted on one of said side arms and adjustable along the arm axis, a mass of non-hydroscopic material mounted on the other side arm and likewise adjustable along the arm axis, a spring opposing angular rotation of said staff by the water vapor content of the hygroscopic material, a pointer member cooperative with said staff and rotatable therewith and a stationary graduated 7 scale cooperative with said pointer member.

2. A direct reading hygrometer as defined in claim 1 wherein said'hygroscopic material is disposed within a containing member and said containing member open to the surrounding air is carried by and adjustable along the axis of the associated side arm.

3. A direct reading hygrometer as defined in claim 1 wherein the hygroscopic material is constituted by a single body disposed within a Wire cage and said cage is carried by and adjustable along the axis of the associated arm.

4. A direct reading hygrometer as defined in claim 1 wherein said hygroscopic material is of granular form contained within a foraminous cup carried by and adjustable along the axis of the associated side arm.

5. A direct reading hygrometer comprising a horizontally disposed staff, a pointer secured to said staff and having oppositely extending side arms, a mass of hygroscopic material mounted on one of said side arms and adjustable along the arm axis, a mass of non-hygroscopic material mounted on the other side arm and likewise adjustable along the arm axis, a spring opposing ang-ular rotation of said staff by the water vapor content of said hygroscopic material, and a graduated scale cooperative with the said pointer.

ANTHONY H. LAMB.

REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Number Name Date 12,071 Ross Dec. 12, 1854 1,173,038 Roschanek Feb. 22, 1916 2,032,306 Pratt Feb. 25, 1936 2,136,618 Hull Nov. 15, 1938 2,235,064 Cloud Mar. 18, 1941 2,255,734 McGrath Sept. 9, 1941 2,268,442 Crawford Dec. 30, 1941 

